1. Field of the Invention
The present invention relates to a hydraulic jack, and more particularly to a joint between a first cylinder and a second cylinder of a hydraulic jack to allow the second cylinder to drive the arm directly.
2. Description of Related Art
A conventional hydraulic jack is shown in FIG. 9, which has a body (30) with multiple rollers (31) rotatably mounted on a bottom of the body (30) to allow the jack to be moved, a cylinder (40) mounted in the body (30) and having a piston rod (43) extendable out of the cylinder (40), a push arm (35) pivotally connected to a free end of the piston rod (43), an arm (32) pivotally connected to a free end of the push arm (35) and having two auxiliary arms (33) oppositely mounted on each side of the arm (32) and a seat (34) mounted on top of the arm (32).
When this conventional hydraulic jack is in application, the piston rod (43) moves in a direction as shown by the arrow, which lifts the arm (32) as well as the two auxiliary arms (33) so that if there is a load on top of the seat (34), the upward movement of the arm (32) will lift the load on top of the seat (34).
However, with careful review of the design of the conventional hydraulic jack, it is noted that when the cylinder (40) is activated, the cylinder (40) applies a horizontal drive to the push arm (35) so as to lift the arm (32). Furthermore, the two auxiliary arms (33) on opposite sides of the arm (32) as well as the push arm (35) take up a great deal of space in the body (30). Therefore, the conventional hydraulic jack is excessively bulky which hinders its practicability.
Furthermore, because the piston rod (43) indirectly drives the arm (32), a great force is required to drive the arm (32).
Further still, because there are multiple joints in the jack, smooth operation of the hydraulic jack is not easy to be sustained.
To overcome the shortcomings, the present invention tends to provide an improved joint between cylinders of a hydraulic jack to mitigate and obviate the aforementioned problems.
The primary objective of the present invention is to provide an improved joint between a first cylinder and a second cylinder of a hydraulic jack so that when pumping the first cylinder, the hydraulic fluid in the first cylinder is able to drive the second cylinder directly.
Another objective of the present invention is that the joint between the second cylinder and the arm is pivotal so that when the second cylinder is activated by the first cylinder, the arm is able to be lifted horizontally relative to the body of the hydraulic jack.
Still another objective of the present invention is to provide a first annular fluid passage and a second fluid passage in the pivotal shaft that is used to connect the first cylinder and the second cylinder so that whenever the pivotal shaft is rotated, hydraulic fluid is able to flow into the second cylinder to lift the arm.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.